The present invention relates to an improved electromagnetic suspension and guidance system for ground vehicles, such as a train.
Prior to the present invention there have been two type of electromagnetic suspension systems. These type of systems may be classified as utilizing repulsive levitation and attractive levitation.
In the repulsive type of levitation a superconducting magnet is carried by the vehicle over a metal plate and induces a current to levitate the vehicle. This type of system has two specific disadvantages. It requires the support of wheels at speeds which are below the speed required to establish the vehicle levitation and the use of the superconducting magnets creates substantial fringe fields in the portions of the vehicle normally occupied by passengers and operators. An example of this type of system can be seen in the U.S. Pat. No. 3,470,828 to J. R. Powell, Jr. et al.
In the attractive type of system levitation is provided by positioning a magnet supported by the vehicle below a portion of a rail, such as the flanges of a T-shaped rail, and allowing the attraction force of the magnet to provide the force of levitation. This system has the disadvantages that it does not use superconducting magnets but uses conventional copper electromagnets and thus is not as efficient as desired and further that the tolerances of construction of the rail and the vehicle have to be very high. Additionally, this systems requires that the forces created for levitation must be adjusted very rapidly for proper operation. In both of these prior art systems, an additional system is added for stabilizing the position of the vehicle with respect to the rails.
Superconducting electromagnets have been known and use in the prior art. Additionally, in the use of such devices in medical apparatus, it has been found that the limiting of the fringe field was desirable and such shielding is taught in the F. R. Huson U.S. Pat. Nos. 4,783,628 and 4,822,772.